Field of the Invention
The present invention relates to a wireless communication, more particularly a method, carried out by a terminal, for transmitting a physical sidelink broadcast channel (PSBCH) in a wireless communication system and the terminal utilizing the method.
Related Art
In International Telecommunication Union Radio communication sector (ITU-R), a standardization task for International Mobile Telecommunication (IMT)-Advanced, that is, the next-generation mobile communication system since the third generation, is in progress. IMT-Advanced sets its goal to support Internet Protocol (IP)-based multimedia services at a data transfer rate of 1 Gbps in the stop and slow-speed moving state and of 100 Mbps in the fast-speed moving state.
3rd Generation Partnership Project (3GPP) is a system standard to satisfy the requirements of IMT-Advanced and is preparing for LTE-Advanced improved from Long Term Evolution (LTE) based on Orthogonal Frequency Division Multiple Access (OFDMA)/Single Carrier-Frequency Division Multiple Access (SC-FDMA) transmission schemes. LTE-Advanced is one of strong candidates for IMT-Advanced.
There is a growing interest in a Device-to-Device (D22) technology in which devices perform direct communication. In particular, D2D has been in the spotlight as a communication technology for a public safety network. A commercial communication network is rapidly changing to LTE, but the current public safety network is basically based on the 2G technology in terms of a collision problem with existing communication standards and a cost. Such a technology gap and a need for improved services are leading to efforts to improve the public safety network.
The public safety network has higher service requirements (reliability and security) than the commercial communication network. In particular, if coverage of cellular communication is not affected or available, the public safety network also requires direct communication between devices, that is, D2D operation.
D2D operation may have various advantages in that it is communication between devices in proximity. For example, D2D UE has a high transfer rate and a low delay and may perform data communication. Furthermore, in D2D operation, traffic concentrated on a base station can be distributed. If D2D UE plays the role of a relay, it may also play the role of extending coverage of a base station.
Meanwhile, D2D action includes D2D discovery and D2D communication. The D2D discovery relates to a process in which a terminal searches for another terminal, and the D2D communication relates to the data communication with the other terminal. Conventionally, when transmitting a D2D discovery signal, the terminal periodically transmits a discovery signal after transmitting the synchronization signal once. Such conventional methods may be appropriate for commercial applications, but are not appropriate for situations where more reliable discovery actions, such as public safety, are required.
Meanwhile, a sidelink process is a process of processing the received D2D signal depending on the D2D action. In view of the terminal receiving the D2D signal, the D2D signal may have various characteristics. For example, the D2D signal synchronized with a certain cell, the D2D signal for relay, and the received quality of the signal may be variously classified depending on the threshold value or the like. It is inefficient to allocate the same sidelink process uniformly for various D2D signals.